A little update about the project status...I've built a prototype of a new switching power supply as suggested by Dario. Below is a picture. I was able to test it at 400mAmps and a Vin Max of 31Volt DC. The output voltage is 5V. I've measured about 200mV of ripple in these conditions. I think it's good and I'll integrate as soon as possible in the target board.

Hello Dario.Sorry for the delay... but my spare time is very limited...

Unfortunately I've not a current probe for the scope so I've modified a little bit the schematics inserting a 1ohm resistor series to the inductor. I've then used two scope channels to measure the voltage across the resistor terminals. I've also placed a multimeter measuring current flowing either on the input side, either on the output side.In the attached picture you can see the results.

Channel1, the yellow line, is the output side voltage (more or less 5V). Channel 2, the cyan line, is the input voltage (an average of 31.4V). Channel3 is the "hot" resistor terminal (the one attached to the inductor), Channel4, the green line, is the resistor on the capacitor side (i.e. it's attached to the same position of CH1 but the sensitivity on this channel is 1V). The red line is the difference between Ch3 and Ch4.With a 1ohm resistor I can imagine to read Amps instead of Volts. Effectively we can see a sawtooth with an averaged value supposed to be a bit less than a half of Ampere.

The Frequency measurement on Ch3 reports that the switching is running at 24.3kHz. It's probably something I can modify changing the capacitor value connected to the switching IC... Probably increasing the frequency will rise up the efficiency... but I've to investigate about.

On the multimeter snapshots, below the scope picture, are the DC and AC current measurements at the input side (on the left) and at the output side (on the right).

the result is pretty nice and close to the maximum efficiency that you can have. Using a linear regulator with 31V input (if it doesn't burn before) has (5V/31V) 16% of efficiency because the input and output current are the same.

The frequency value is related to the power loss, bigger is the frequency lower is the efficiency. This because this type of devices has losses during the switching phase, rather during the ON or OFF phase the power that is lost is pretty low. On the other side, bigger frequencies gives you a lower ripple.

You may try to increase the efficiency with a lower frequency and a bigger output capacity, but I think that your result are good and also the output voltage is stable.

Thanks for sharing.

Regards,Dario.

Souliss - Open-source Distributed Home Automation with Arduino and Android

In the meantime I would like to update this thread with the new schematics and the board layout.In this new revision is the switching power supply and the UEXT connector. This will not be populated but it will be available for users that like this type of expansion connector. The two I2C pull-up resistors will be soldered on but left unconnected from the 3v3 through the SJ2 placed on the back side. I'm thinking that probably the best solution would be to have a SJ for each resistor instead of a single SJ2 in series with the 3.3V. This will prevents a series resitor connections between SCL and SDA lines when UEXT is not used. I'll do it.The PD5 line is used as slave select in the SPI related part of UEXT connector. This connector receives, as required by the UEXT documentation, the 3.3V generated by IC6.

Lastly, the three relays and related LEDs are directly connected to the Vin.

I think that your board will be very interesting and I hope to have the RS485 drivers running on Souliss as soon. It will be a nice work, because I shall build a P2P over RS485 and so means have a collision management done at software side.

In Souliss, we are planning the new release by the end of the June or earlier July. The new release shall contain the support for ENC28J60, a new scheduler, anti-theft logics and some general improvement and bugfix. After, we will start for the new features that will include: RS485 drivers, Ethernet-MAC support (to skip IP configuration) and a binary protocol for the external interfaces.

In the while, we are working with the Freedomotic team for the integration between Souliss and Freedomotic, using a plugin on the freeedomotic side (JSON), and I hope to be able to release also a new web-based user interface.

Thanks for sharing your work.

Regards,Dario.

Souliss - Open-source Distributed Home Automation with Arduino and Android

Hi Dario.I'll send you in a short time a prototype. Unfortunately actually I have only one unit in my hands (I built two units but one is actually out of the office and will be back in a few days (I hope))... but I think you're more interested in the new version with UEXT connector... so we have to wait for the PCB production and assembly.

In the meantime I'm thinking to a new other object that I think could help Freedomotic and Souliss to have a more impact on domotic systems. Let's imagine to have a board could be easily connected to pushbuttons and/or switches like the one provided by Living Series or similar. A board with ATMEGA328, power supply and the RS485 bus logic onboard, with LEDs (RGB?) placed in the proper position in order to be fitted in the Living pushbuttons hole for status indication... Something like a piggy back for three standard switches...

Let's imagine to have a board could be easily connected to pushbuttons and/or switches like the one provided by Living Series or similar. A board with ATMEGA328, power supply and the RS485 bus logic onboard, with LEDs (RGB?) placed in the proper position in order to be fitted in the Living pushbuttons hole for status indication... Something like a piggy back for three standard switches...

Great idea Marco. I'm following your thread since the beginning. Unfortunately I have no such experience in this field in order to be able to contribute.

I've the hardware to start the development of the RS485 drivers, so don't worry for the time required to get the PCBs. Now for me is just a matter of time, because I've some pending activities before the release of the next Souliss and only after I may start the development of RS485 and other features.If you will open a new topic, I will be in the chat

<IMHO>Regarding the new proposal for others boards, let me say that compete with the Big of the automation is too hard, if you want to win or at least stay alive, the easy way is propose something different. This is why Souliss has a different approach that is not found in the commercial automation systems.On my side, I think that the actual commercial products are not strong enough on the small installation, where you have to spent an huge amount of money compared to the home size. In a big home the ration looks different.

On my side I think that the hardwired pushbutton, in a modern automated home, shall be less as possible. Maybe, you have it all in one remote location, used only when required. Sensors like PIRs and mobile devices may act for this.

To lower the price of the automation system, I think that the option shall be use less board with high density of I/O, rather than boards in each junction box. It require more cabling, but in a small home shall not be a problem.</IMHO>

I've an idea to propose, dimming is something "cool" but use old fashing lights has no meaning, play with high power LEDs is more interesting. I think that on the market there aren't LEDs power supply that can be easily included in an home automation system, I was working to a power supply that may interact with Souliss (RS485, Wireless 2.4 GHz or Ethernet).

I've tried to find out a commercial power supply that was easy to interface with a board (the best was dimmed via analog output), but I've found nothing as now.

Is this something that look interesting to you?

Thanks again for your sharing.

Regards,Dario.

Souliss - Open-source Distributed Home Automation with Arduino and Android

@Flx: Thank you for sharing your opinion. It's not important if you don't have so much experience in developing boards and/or schematics. Here we are for share ideas... and all contributes are really appreciated. The success of a product is not strictly related to technical solutions but more on ideas! So you're welcome!

@Dario: I don't want (can't) compete with big players. I would like to develop objects targeted to DIY fans. I can tell you an example... my house. The electric plan was built following the conventional style. No domotics, no other goodies. Being a DIY-man I would like to add some domotics functions... but this requires to change all switches and much more. So I was thinking about re-use the electrical hardware (that not only costs a lot... but is also beautiful and I like it!). I can then re-use the electric junction boxes disseminated through the home to install actuators... all could be connected through a 485 bus and probably integrated with the ethernet equipment through a gateway for controlling/supervising. I'll be able to program it because each "agent" in the system contains open software. I think that there are a lot of people that love this approach in the Community and could be interested in this type of products that, sure, will not demote the Souliss approach but can help integration through a "classic" human interface.

For what's related to High Power LEDs: it's something I started to follow some years ago (there is a Circuit Cellar's article I wrote, where I used a dsPIC to drive three 1Watt LEDs in a three channel psychedelic lights project http://www.scribd.com/doc/50577471/CC-248-2011). I'm interested on this type of project and it's something I would like to propose. We can start a new thread to understand what are the requirements.Have you checked the High Power LED Shield proposed on the www.EtherMania.com website? It's a four channel 350mA constant current driver for High Power LEDs. LEDs could be dimmered through the Arduino PWM channels. http://www.ethermania.com/shop/index.php?main_page=product_info&cPath=91_104&products_id=1176&language=en It could be a good starting point... but I think we are OT on this thread (sorry for the link-spamming).

I'm planning to use the T7SS5E6-24. I've already used the 5V version without problem in these years and I like it.They have a 360mW coil consumption so I can calculate a 15mA for the 24V version... (quite like a normal LED). Having three of that + LEDs I suspect we are in the range of a 100mA at full load.I think we can also reduce the coil dimension used in the last PCB because I suspect that nobody needs a 0.4Amps on the 5V... and probably reduce the switching output capacitor.

But... speaking about DC and power related... I'm thinking to something that could help to have an easy deploy of these items in the house. I'm thinking to merge the data and power on the same line. What do you think to have a carrier modulated injected over the DC line? I'm thinking to something like DTMF tones or the "simplest" FSK. I'm quite sure we can do something like what was used in the sotware modem library for Arduino: